1. Field of the Invention
This invention relates to systems and methods of transmit diversity for wireless communication, and particularly, to a system and method for wireless communication by employing a transmit diversity technique in a wireless multiple-input multiple-output (MIMO) system.
2. Description of Related Art
With the rapid development of communication technology, providing high-speed and reliable transmission services is becoming one of the most popular issues in the art. A multi-input multi-output (MIMO) wireless communication technique uses a plurality of antennas in a transmitting terminal and a receiving terminal, and may be applied to improve the performance of wireless mobile Internet services and next-generation cellular systems.
Currently, in an MIMO wireless communication system a diversity technique is proposed to increase the transmission reliability of the wireless communication system. The diversity technique of the transmission terminal may be categorized into three groups. The first one evaluates channels in the receiving terminal, and feeds messages back to the transmitting terminal. The second one uses a space time code or space frequency code technique. The third one uses a maximum ratio transmission technique. The aforesaid three techniques operate based on a condition that the receiving terminal and the transmitting terminal know the channel state information. Additionally, U.S. Pat. No. 7,362,823 B2 proposed a diversity algorithm that transmits and receives information under a condition that both the transmitting terminal and the receiving terminal have channel state information. U.S. Pat. No. 7,107,021 B2 disclosed an antenna-switching technique that is applied to a code division multiple access (CDMA) system, by measuring the power of signals with the receiving terminal and feeding the result back to the transmitting terminal, so as to obtain a diversity effect. Taiwanese patent No. 588520 and No. I298588 disclosed a diversity reception device that evaluates channels in the receiving terminal, so as to achieve the diversity effect.
The transmitting terminal and receiving terminal may be a base station or a user-end electronic device, for example. However, a receptor of a general user, such as a smart phone, notebook computer or personal digital assistant (PDA), has to have a simpler design, as compared with a base station. The receiving terminal's requesting the evaluation of channel state information may complicate the operation and hardware of the receiving terminal. Besides, the receiving terminal has to transmit the evaluation result or measured power back to the transmitting terminal, which sacrifices the communication capacity of both the receiving terminal and the transmitting terminal.
Therefore, how to provide a system and method for wirelessly transmitting and receiving information under a condition that the receiving terminal does not know the channel state information, so as to bring the spatial diversity technique of the receiving terminal into practice, not to consume the efficacy of the communication system and to greatly simplify the hardware and algorithm of the receiving terminal is becoming one of the most popular issues in the art.